Audience: Patients and carers. Published 11 November 2026 (AEDT). Study published: 9 November 2026.
Weight-loss medicines such as tirzepatide can lead to large weight loss, but some of the weight lost is lean tissue, which includes muscle. A new Australian randomised trial, published in the peer-reviewed journal Nature Medicine, tested whether supervised weight training could reduce that loss and protect strength.
What did the study do?
Researchers at the University of Western Australia enrolled 120 adults aged 50 to 70 (men and post-menopausal women) living with obesity, or overweight plus a weight-related condition. People with diabetes or heart disease were not included, and participants were doing little exercise beforehand. Everyone received weekly tirzepatide injections for 40 weeks. Half were randomly assigned to three one-hour, supervised resistance (weight) training sessions a week; the other half continued their usual activities. Body composition was measured with DXA scans.
What did it find?
Both groups lost a similar amount of weight: about 22.6 kg without training and 22.3 kg with training, mostly fat (about 17 to 18 kg). The difference was in lean tissue. People who did not train lost an average of 4.7 kg of lean tissue, compared with 3.6 kg in the training group, about 1.1 kg less, or roughly a quarter less. Training reduced lean tissue loss but did not stop it.
Strength showed a clearer difference. Without training, strength in three gym tests fell by about 6 to 9%. With training, it rose by about 11 to 18%. Side effects such as nausea were common in both groups and occurred at similar rates. Nine people (7%) did not complete the study, six of them because of side effects.
What remains uncertain?
This was a single, fairly small study. The training was supervised by accredited exercise physiologists in a research gym, and attendance was very high, which may be hard to match in everyday life. Results may not apply to younger people, people with diabetes or heart disease, or people using other weight-loss medicines. The study did not measure longer-term outcomes such as falls, frailty or quality of life, and the staff testing strength knew who was training. The drug maker supplied the medicine free of charge, and several authors have received speaker fees from it.
What this may mean
For people using a weight-loss medicine, the study supports talking with a GP about keeping muscle strength in mind, including whether resistance exercise suits them and what kind of support is available. Anyone with health conditions, joint problems or concerns should get advice before starting a new exercise program.
Prepared with AI assistance from the published study and the news report linked below. No clinical review by the ATM Health editorial team is claimed. General information only, not individual medical advice.
Sources
newsGP (RACGP): Resistance training slashes muscle loss for GLP-1 patients: Study (10 November 2026). Accessed 11 November 2026 (AEDT).